Two-component spray device and use thereof

ABSTRACT

This invention is directed to a spray device for spraying two or more components. The two or more components are maintained separated in the spray device and are mixed post atomization. This invention is also directed to a gravity fed spray gun and a system for spraying two or more components. This invention is further directed to a kit for converting an existing conventional single-component spray gun typically used for spraying a single component to a two-component spray gun for spraying two components.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/US2010/053294, filed Oct. 20, 2010, which was published under PCTArticle 21(2), and which claims priority from U.S. ProvisionalApplication Ser. No. 61/304,524 (filed Feb. 15, 2010), the disclosuresof which are incorporated by reference herein for all purposes as iffully set forth.

FIELD OF INVENTION

The present invention is directed to a spray device for spraying two ormore components. This invention is specifically directed to a spraydevice for spraying a coating composition having two or more components.

BACKGROUND OF INVENTION

Coatings on automotives or other objects typically comprise polymernetworks formed by multiple reactive components of a coatingcomposition. The coatings are typically applied over a substrate such asautomobile vehicle body or body parts using a spray device or othercoating application techniques and then cured to form a coating layerhaving such polymer networks.

Currently, the multiple reactive components of the coating compositionare typically mixed together to form a pot mix prior to spraying andplaced in a cup-like reservoir or container that is attached to aspraying device such as a spray gun. Due to the reactive nature of themultiple reactive components, the pot mix will start to react as soon asthey are mixed together causing continued increase in viscosity of thepot mix. Once the viscosity reaches a certain point, the pot mix becomespractically un-sprayable. The possibility that the spray gun itself maybecome clogged with crosslinked polymer materials is alsodisadvantageous. The time it takes for the viscosity to increase to suchpoint where spraying becomes ineffective, generally a two-fold increasein viscosity, is referred to as “pot life”.

One way to extend “pot life” is to add a greater amount of thinningsolvent, also known as thinning agent, to the pot mix. However, thinningagent, such as organic solvent, can contribute to increased emissions ofvolatile organic compounds (VOC) and can also increase curing time.

Other attempts to extend “pot life” of a pot mix of a coatingcomposition have focused on “chemical-based” solutions. For example, ithas been suggested to include modifications of one or more of thereactive components or certain additives that would retardpolymerization reaction of the multiple components in the pot mix. Themodifications or additives must be such that the rate of curing is notadversely affected after the coating is applied to the surface of asubstrate.

Another approach is to mix one or more key components, such as acatalyst, together with other components of the coating compositionimmediately prior to spraying. One example is described in U.S. Pat. No.7,201,289 in that a catalyst solution is stored in a separate dispenserand being dispensed and mixed with a liquid coating formulation beforethe coating formulation is atomized.

Yet another approach is to separately atomize two components, such as acatalyst and a resin, of a coating composition, and mix the two atomizedcomponents after spray. One such example is described in U.S. Pat. No.4,824,017. However, such approach requires atomization of two componentsseparately by using separate pumps and injection means for each of thetwo components.

STATEMENT OF INVENTION

This invention is directed to a spray gun for spraying a coatingcomposition comprising a first component and a second component, saidspray gun comprising:

-   -   (A) a spray gun body (1) comprising a carrier inlet (12), a        first inlet (10) connected to a first connection path (10 a);    -   (B) a tubular nozzle casing (6) having a nozzle (13), said        tubular nozzle casing being housed within said spray gun body        (1);    -   (C) a hollow spray needle (9) having a longitudinal channel (9        a) therein, a channel opening (13 a) at one end of said hollow        spray needle, and a second inlet (8) at the other end of said        hollow spray needle distal to said channel opening (13 a),        wherein at least a portion of said hollow spray needle (9) is        housed in said tubular nozzle casing (6) and said hollow spray        needle (9) is configured to slide in said tubular nozzle casing        (6) between a spray position and a closed position;    -   (D) an inlet valve for controlling said second inlet (8); and    -   (E) a detachable coupling assembly (18) affixed externally to        said spray gun body distal to said nozzle; wherein said second        inlet (8), said inlet valve and said detachable coupling        assembly are configured so that said second inlet is open at        said spray position and is closed at said closed position;    -   wherein:    -   said first component and said second component are maintained        separated in said spray gun;    -   said first inlet is configured to receive said first component        by gravity and connected to said first connection path that is        further connected to a spray passage defined by said tubular        nozzle casing and said hollow spray needle for conveying said        first component to said nozzle; and    -   said second inlet is configured to receive said second component        by gravity and connected to said longitudinal channel for        conveying said second component to said nozzle when said hollow        spray needle is at said spray position.

This invention is also directed to a kit for converting a spray gun tospray a coating composition having a first component and a secondcomponent, said kit comprising:

-   -   (a) a hollow spray needle (9) having a longitudinal channel (9        a) therein, a channel opening (13 a) at one end of said hollow        spray needle, and a second inlet (8) at the other end of said        hollow spray needle distal to said channel opening (13 a);    -   (b) an inlet valve for controlling said second inlet (8); and    -   (c) a detachable coupling assembly (18), wherein:    -   when assembled to said spray gun, at least a portion of said        hollow spray needle (9) is housed in a tubular nozzle casing (6)        and functionally coupled to a trigger (22) of said spray gun,        and said hollow spray needle (9) is configured to slide in said        tubular nozzle casing (6) between a spray position and a closed        position as controlled by said trigger (22); said second inlet        (8), said inlet valve and said detachable coupling assembly (18)        are configured so that said second inlet is open at said spray        position and is closed at said closed position.

This invention is also directed to a method using the spray gun of thisinvention for producing a layer of a coating composition comprising afirst component and a second component on a substrate.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 shows a schematic presentation of an example of a spray gun ofthis invention.

FIG. 2 shows schematic presentations of an example of a spray gun havinga hollow spray needle, an inlet valve and a detachable couplingassembly. (A) The hollow spray needle at the closed position. (B) Thehollow spray needle at the spray position. (C) Schematic presentationsof an example of the hollow spray needle, inlet valve and the detachablecoupling assembly.

FIG. 3 shows schematic presentations of another example of a spray gunhaving a hollow spray needle, an inlet valve and a detachable couplingassembly. (A) The hollow spray needle at the closed position. (B) Thehollow spray needle at the spray position. (C) Schematic presentationsof another example of the hollow spray needle, the inlet valve and thedetachable coupling assembly.

FIG. 4 shows a frontal view of an example of a nozzle-air cap assembly.(A) Frontal view. (B) Details of the frontal view

FIG. 5 shows schematic presentations of examples for filling the secondreservoir, (A) Filling the second reservoir via gravity. (B) Filling thesecond reservoir using a pump.

FIG. 6 shows schematic presentations of examples of the flow indicator.(A) and (B) Schematic presentations of flow indicators (11 b) attachedto the second connection coupling (11) in various examples ofconfigurations. (C) Schematic presentation of an example of the flowindicator with one or more flaps (110). (D) Schematic presentation of anexample of the flow indicator with one or more wheels (111). (E)Schematic presentation of an example of an electronic flow indicator(112).

DETAILED DESCRIPTION

The features and advantages of the present invention will be morereadily understood, by those of ordinary skill in the art, from readingthe following detailed description. It is to be appreciated that certainfeatures of the invention, which are, for clarity, described above andbelow in the context of separate embodiments, may also be provided incombination in a single embodiment. Conversely, various features of theinvention that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any sub-combination.In addition, references in the singular may also include the plural (forexample, “a” and “an” may refer to one, or one or more) unless thecontext specifically states otherwise.

The use of numerical values in the various ranges specified in thisapplication, unless expressly indicated otherwise, are stated asapproximations as though the minimum and maximum values within thestated ranges were both proceeded by the word “about.” In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as values within the ranges.Also, the disclosure of these ranges is intended as a continuous rangeincluding every value between the minimum and maximum values.

As used herein:

“Two-pack coating composition”, also known as 2K coating composition,means a thermoset coating composition comprising two components that arestored in separate containers, which are typically sealed for increasingthe shelf life of the components of the coating composition. Thecomponents are mixed just prior to use to form a pot mix, which has alimited pot life, typically from few minutes, such as 15 minutes to 45minutes, to few hours, such as 4 hours to 10 hours. The pot mix isapplied as a layer of desired thickness on a substrate surface, such asthe body or body parts of a vehicle. After application, the layer driesand cures to form a coating on the substrate surface having desiredcoating properties, such as, desired gloss, mar-resistance, resistanceto environmental etching and resistance to degradation by solvent. Atypical two-pack coating composition can comprise a crosslinkablecomponent and a crosslinking component.

“One-Pack coating composition”, also known as 1K coating composition,means a coating composition comprises multiple ingredients mixed in onesingle package. A one-pack coating composition can form a coating layerunder certain conditions. One example of 1K coating composition cancomprise a blocked crosslinking agent that can be activated undercertain conditions. One example of the blocked crosslinking agent can bea blocked isocyanate. Another example of 1K coating composition can be aultraviolet (UV) radiation curable coating composition.

The term “radiation”, “irradiation” or “actinic radiation” meansradiation that causes, in the presence of a photo initiator,polymerization of monomers that have polymerizable ethylenicallyunsaturated double bonds, such as acrylic or methacrylic double bonds.Sources of actinic radiation may be natural sunlight or artificialradiation sources. Other examples of radiation can includeelectron-beam, also known as e-beam. A coating curable by radiation,such as UV, can be referred to as a radiation coating or a UV coating. AUV coating can be typically a 1K coating. A UV curable coating cantypically have a UV curable component comprising monomers that havepolymerizable ethylenically unsaturated double bonds, such as acrylic ormethacrylic double bonds; and one or more photo initiators or radiationactivators. Typically, a 1K coating composition, for example a UVmono-cure coating composition, can be prepared to form a pot mix andstored in a sealed container. As long as said UV mono-cure coatingcomposition is not exposed to UV radiation, said UV mono-cure coatingcomposition can have indefinite pot life.

A coating that can be cured by one curing mechanism, such as by chemicalcrosslinking alone or by UV radiation alone, can be referred to as amono-cure coating. A coating that can be cured by both chemical andradiation, such as by both chemical crosslinking and UV radiation, canbe referred to as a dual-cure coating.

“Low VOC coating composition” means a coating composition that includesless than 0.6 kilograms per liter (5 pounds per gallon), preferably lessthan 0.53 kilograms (4.4 pounds per gallon) of volatile organiccomponent, such as certain organic solvents. The phrase “volatileorganic component” is herein referred to as VOC. VOC level is determinedunder the procedure provided in ASTM D3960.

“Crosslinkable component” includes a compound, oligomer, polymer orcopolymer having functional crosslinkable groups positioned in eachmolecule of the compound, oligomer, the backbone of the polymer, pendantfrom the backbone of the polymer, terminally positioned on the backboneof the polymer, or a combination thereof. One of ordinary skill in theart would recognize that certain crosslinkable group combinations wouldbe excluded from the crosslinkable component of the present invention,since, if present, these combinations would crosslink among themselves(self-crosslink), thereby destroying their ability to crosslink with thecrosslinking groups in the crosslinking components defined below.

Typical crosslinkable component can have on an average 2 to 25,preferably 2 to 15, more preferably 2 to 5, even more preferably 2 to 3,crosslinkable groups selected from hydroxyl, acetoacetoxy, carboxyl,primary amine, secondary amine, epoxy, anhydride, imino, ketimine,aldimine, or a combination thereof.

The crosslinkable component can have protected crosslinkable groups. The“protected” crosslinkable groups are not immediately available forcuring with crosslinking groups, but first must undergo a reaction toproduce the crosslinkable groups. Examples of suitable protectedcrosslinkable components having protected crosslinkable groups caninclude, for example, amide acetal, orthocarbonate, orthoacetate,orthoformate, spiroorthoester, orthosilicate, oxazolidine orcombinations thereof.

The protected crosslinkable groups generally are not crosslinkablewithout an additional chemical transformation. The chemicaltransformation for these groups can be a deprotection reaction such ashydrolysis reaction that unprotects the group to form a crosslinkablegroup that can then be reacted with the crosslinking component toproduce a crosslinked network. Each one of these protected groups, uponthe deprotection reaction, forms at least one crosslinkable group. Forexample, upon hydrolysis, an amide acetal can form an amide diol or oneof two amino alcohols. As another example, the hydrolysis of anorthoacetate can form a hydroxyl group.

The crosslinkable component can contain compounds, oligomers and/orpolymers that have crosslinkable functional groups that do not need toundergo a chemical reaction to produce the crosslinkable group. Suchcrosslinkable groups are known in the art and can include, for example,hydroxyl, acetoacetoxy, thiol, carboxyl, primary amine, secondary amine,epoxy, anhydride, imino, ketimine, aldimine, silane, aspartate or asuitable combination thereof.

Suitable activators for deprotecting the protected crosslinkablecomponent can include, for example, water, water and acid, organic acidsor a combination thereof. In one embodiment, water or a combination ofwater and acid can be used as an activator to deprotect thecrosslinkable component. For example, water or water with acid can be anactivator for a coating described in POT publication WO2005/092934,published on Oct. 6, 2005, wherein water activates hydroxyl groups byhydrolyzing orthoformate groups that block the hydroxyl groups fromreacting with crosslinking functional groups.

“Crosslinking component” is a component that includes a compound,oligomer, polymer or copolymer having crosslinking functional groupspositioned in each molecule of the compound, oligomer, the backbone ofthe polymer, pendant from the backbone of the polymer, terminallypositioned on the backbone of the polymer, or a combination thereof,wherein these functional groups are capable of crosslinking with thecrosslinkable functional groups on the crosslinkable component (duringthe curing step) to produce a coating in the form of crosslinkedstructures or networks. One of ordinary skill in the art would recognizethat certain crosslinking group/crosslinkable group combinations wouldbe excluded from the present invention, since they would fail tocrosslink and produce the film forming crosslinked structures ornetworks.

Typical crosslinking component can be selected from a compound,oligomer, polymer or copolymer having crosslinking functional groupsselected from the group consisting of isocyanate, amine, ketimine,melamine, epoxy, polyacid, anhydride, and a combination thereof. Itwould be clear to one of ordinary skill in the art that generallycertain crosslinking groups from crosslinking components crosslink withcertain crosslinkable groups from the crosslinkable components.

A coating composition can further comprise a catalyst, an initiator, anactivator, a curing agent, or a combination thereof. A coatingcomposition can also comprise a radiation activator if the coatingcomposition is a radiation curable coating composition, such as a UVcurable coating composition.

A catalyst can initiate or promote the reaction between reactants, suchas crosslinkable functional groups of a crosslinkable component andcrosslinking functional groups of a crosslinking component of a coatingcomposition. A wide variety of catalysts can be used, such as, tincompounds, including organotin compounds such as dibutyl tin dilaurate;or tertiary amines, such as, triethylenediamine. These catalysts can beused alone or in conjunction with carboxylic acids, such as, aceticacid. One example of commercially available catalysts is dibutyl tindilaurate as Fascat® series sold by Arkema, Bristol, Pa., underrespective trademark.

An activator can activate one or more components of a coatingcomposition. For example, water can be an activator for a coatingdescribed in PCT publication WO20051092934, published on Oct. 6, 2005,wherein water activates hydroxyl groups by hydrolyzing orthoformategroups that block the hydroxyl groups from reacting with crosslinkingfunctional groups.

An initiator can initiate one or more reactions. Examples can includephoto initiators and/or sensitizers that cause photopolymerization orcuring of a radiation curable coating composition, such as a UV curablecoating composition upon radiation, such as UV irradiation. Many photoinitiators are known to those skilled in the art and can be suitable forthis invention.

A radiation activator can be activated by radiation and then initiate orcatalyze subsequent one or more reactions. One example can bephotolatent catalyst available from Ciba Specialty Chemicals.

A curing agent can react with other components of a coating compositionto cure the coating composition into a coating. For example, acrosslinking component, such as isocyanate, can be a curing agent for acoating comprising a crosslinkable hydroxyl component. On the otherhand, a crosslinkable component can be a curing agent for a crosslinkingcomponent.

In conventional coating practice, components of a two-pack coatingcomposition are mixed immediately prior to spraying to form a pot mixwhich has a limited pot life, wherein said components can include acrosslinking component, a crosslinkable component, necessary catalysts,and other components necessary as determined by those skilled in theart. In addition to the limited pot life, many catalysts can change itsactivity in the pot mix. For example, some catalysts can be sensitive tothe trace amount of water in the pot mix since water can causehydrolysis and hence inactivation of the catalyst.

This invention is directed to a spray gun for spraying a coatingcomposition comprising a first component and a second component onto asubstrate. The spray gun can comprise:

(A) a spray gun body (1) comprising a carrier inlet (12), a first inlet(10) connected to a first connection path (10 a);

(B) a tubular nozzle casing (6) having a nozzle (13), said tubularnozzle casing being housed within said spray gun body (1);

(C) a hollow spray needle (9) having a longitudinal channel (9 a)therein, a channel opening (13 a) at one end of said hollow sprayneedle, and a second inlet (8) at the other end of said hollow sprayneedle distal to said channel opening (13 a), wherein said hollow sprayneedle (9) is partially positioned and is slidable in said tubularnozzle casing (6) between a spray position and a closed position;

(D) an inlet valve for controlling said second inlet (8); and

(E) a detachable coupling assembly (18) affixed externally to said spraygun body distal to said nozzle; wherein said second inlet (8), saidinlet valve and said detachable coupling assembly are configured so thatsaid second inlet is open at said spray position and is closed at saidclosed position;

wherein:

said first component and said second component are maintained separatedin said spray gun;

said first inlet is configured to receive said first component bygravity and connected to said first connection path that is furtherconnected to a spray passage defined by said tubular nozzle casing andsaid hollow spray needle for conveying said first component to saidnozzle; and

said second inlet is configured to receive said second component bygravity and connected to said longitudinal channel for conveying saidsecond component to said nozzle when said hollow spray needle is at saidspray position.

The spray gun can further comprise a main reservoir (3) (FIG. 1) forconveying said first component to said first inlet by gravity. The spraygun can further comprise a second reservoir (4) for conveying saidsecond component to said second inlet by gravity. The spray gun canfurther comprise a flow control means (11 a) coupled to the second inletfor regulating flow of the second component. The flow control means canbe a valve, a flow restrictor, a quick dry connector, or any otherdevices that can control flow rate.

The detachable coupling assembly (18) can comprise a frame for attachingto the spray gun, a second connection coupling (11) for connecting tothe second reservoir, a valve coupling for controlling the second inlet(8), and one or more fasteners, such as those shown as 18 b, 18 d, 18 b′or 18 d′ for attaching or adjusting the position of the valve couplingto the frame. In one example, the detachable coupling assembly can havea wedge frame (18 a) (FIGS. 2A, 2B and 2C) and a wedge valve coupling(18 c). In another example, the frame can be a sliding frame (18 a′)(FIGS. 3A, 3B and 3C) and a sliding valve coupling (18 c′). The valvecoupling (18 c or 18 c′) can be used in combination with the inlet valeto control the second inlet (8). When the hollow spray needle is at theclosed position, the valve coupling (18 c or 18 c′) can cause the inletvalve, and hence second inlet (8) to be closed. When the hollow sprayneedle is at the spray position, the valve coupling (18 c or 18 c′) cancause the inlet valve, and hence the second inlet (8) to be open.

The inlet valve can be selected from a pin valve, a sliding valve, or acombination thereof. The pin valve can comprise a seal pin (16) that ispositioned at the second inlet (8) with at least a portion of the sealpin seated within the second inlet (8) perpendicular to the hollow sprayneedle and can be moved in the direction perpendicular to thelongitudinal axis of the hollow spray needle. The seal pin can be seatedat the second inlet (8) in a seated position to seal the second inlet sothe second inlet is closed. A spring means can be used to maintain theseal pin at the seated position when the hollow spray needle is not atthe spray position. The seal pin can also partial seal the second inlet.The seal pin can be moved to an open position causing the second inletto be open. The seal pin can be moved by the valve coupling (18 c). Oneexample of the configuration is shown in FIG. 2 with the seal pin (16)in the seated position and the second inlet closed (FIG. 2A), or withthe seal pin (16) in the open position and the second inlet open (FIG.2B). When the second inlet is open, the longitudinal channel (9 a) canbe connected with the second connection coupling and the secondreservoir so the second component can flow into the longitudinal channeland be sprayed out of the nozzle. When the second inlet is closed, thelongitudinal channel can be disconnected with the second connectioncoupling and the second reservoir so the second component can not flowinto the longitudinal channel.

The sliding valve can comprise a seal sleeve. The seal sleeve can be astand alone part or be a part of the valve coupling. The sliding valvecan slide between a closed valve position and an open valve position.When the sliding valve is at the closed valve position, the second inlet(8) and the second connection coupling (11) are misaligned causing thesecond inlet to be closed. When the sliding valve is at the open valveposition, the second inlet (8) and the second connection coupling (11)are aligned causing the second inlet to be open. The hollow spray needleand the sliding valve can be assembled and configured in such a way sothat the sliding valve is at the closed valve position when the hollowspray needle is at the closed position (FIG. 3A) and the sliding valveis at the open valve position when the hollow spray needle is at thespray position (FIG. 3B). One example of the seal sleeve can be thesliding valve coupling (18 c′) as shown in FIG. 3C. The sliding valvecoupling (18 c′) can be assembled into the sliding frame (18 a′) and canbe configured or adjusted via one or more fasteners (18 b′ and 18 d′).

As shown in FIG. 1, the spray gun body (1) can have additional multipleparts, controls, such as carrier coupling (12) for coupling to a sourceof a carrier, such as compressed air; a carrier regulator assembly (25)for regulating and measuring flow rate and pressure of the carrier; acoating flow regulator (not shown) for regulating flow of the firstcomponent that is stored in a main reservoir (3), and other mechanismsnecessary for proper operation of a spray gun known to those skilled inthe art. Additional control or parts can include, such as a trigger (22)and a spray fan regulator (20) for regulating compressed carrier such ascompressed air jetting out from a set of shaping air jets (24 a) (FIGS.4A and 4B) for forming desired spray shape, such as a fan-shape.Typically, multiple channels, connectors, connection paths andmechanical controls can be assembled within the spray gun body. Thespray gun body can also provide further assembly or operation mechanismsfor additional parts or controls, such as an air cap (24) that can forma spray nozzle-air cap assembly (2). The carrier can be discharged fromthe space (24 b) defined by the air cap and the nozzle (13) (FIG. 48).

The spray passage can be configured to disconnect from said firstconnection path when said hollow spray needle is at said closedposition. Both the longitudinal channel and the spray passage can beconfigured to disconnect at the same time when said hollow spray needleis at said closed position: the longitudinal channel can be configuredto disconnect from said second connection coupling and said spraypassage can be configured to disconnect from said first connection path.

The tubular nozzle casing or said hollow spray needle can have a taperedopening at the nozzle and the hollow spray needle can be configured toseal the nozzle at said closed position. Some examples are shown inFIGS. 2A, 2B, 3A and 3B.

The hollow spray needle (9) can be sliding in the bi-direction shown bythe bi-directional arrow (23) and can be configured to cause controlledconnections between the longitudinal channel and the second connectioncoupling: the longitudinal channel can be disconnected from said secondconnection coupling when said hollow spray needle is at said closedposition and the longitudinal channel can be connected to said secondconnection coupling when said hollow spray needle is at said sprayposition.

The first inlet (10) can be constructed or configured onto the spray gunbody through means known to those skilled in the art. The first inlet isconnected to the nozzle for conveying a first component of the coatingcomposition to the nozzle. The main reservoir (3) is not pressurized andthe first inlet can be typically positioned at the upper side of thespray gun body so the first component can be conveyed to the firs inletand further into the spray gun by gravity during normal spray operation,such as hand-held spraying. The spray gun can comprise a secondreservoir (4) for conveying a second component to the second inlet bygravity during normal spray operation, such as hand-held spraying. Thesecond reservoir can be positioned separately from the main reservoir(3) (FIG. 1). The reservoirs can be attached to the spray gun body usingadaptors, couplings, or flow control means. In one example, a connectorcan be coupled to the second inlet (8) for easy connection, flow ratecontrol, or a combination thereof. One example of the connector can be aquick dry connector. Additional couplings, connectors, adaptors can alsobe used.

The second reservoir (4) can comprise a hard capsule having fixed shapeor volume, a collapsible enclosure having flexible shape or volume, or acombination thereof. In one example, a combination of a hard capsule anda collapsible enclosure (4 a) can be suitable. The second reservoir (4)can further comprise a transparent opening (4 b) for easy monitoring ofthe contents within. The second reservoir (4) can comprise a sensor tomonitor the contents within. The purpose of the transparent opening (4b) or the sensor is to provide warning to an operator when the secondreservoir (4) is empty. The hard capsule can made of plastic, metal,glass, or a combination thereof. The collapsible enclosure (4 a) can bemade from plastic or other flexible materials. The hard capsule can beventilated. The second reservoir can be filled with a master container(51) by gravity (FIG. 5A) via a set of connection tubing (52), one ormore connection couplings (55), and one or more flow control devices (53or 54). The second reservoir can also be filled with a master container(51) using a power source, such as a pump (56) (FIG. 5B). It ispreferred that the air in the collapsible enclosure (4 a) is removedprior to filling to avoid trapping air bubbles with in. The one or moreconnection couplings can be a quick dry connector or any other typeseasy connectors to minimize trapping air or spill the content.

The spray gun can further comprise a flow indicator (11 b, FIGS. 6A and6B) or a combination of the flow indicator (11 b) and the flow controlmeans (11 a). The flow indicator can be a stand alone device, a part of,or a combination of any of the adaptors, couplings, or connectors. Inone example, the flow indicator (11 b) can be combined with the secondconnection coupling (11). In another example, the flow indicator can bepart of the second reservoir (4). In yet another example, the flowindicator can be used in combination with the flow control means (11 a).In yet another example, the flow indicator can be used in combinationwith the flow control means (11 a) and the second connection coupling(11). The flow indicator can be selected from a visual flow indicator,an electronic flow indicator, or a combination thereof.

The visual flow indicator can comprise an indicator body (60) and anindicator means. The indicator means can comprise one or moretransparent windows (61), one or more flaps (62), one or more wheels(64), one or more visual markers (66), or a combination thereof. In oneexample, the flow indicator can comprise an indicator body and atransparent window. The flow of the second component as indicated by thearrow (120) can be viewed through the transparent window. In anotherexample, the flow indicator (110) (FIG. 6C) can comprise a flap (62).When the second component is flowing through, the flap can be forced bythe flow to change position as indicated by the arrow (63). In yetanother example, the flow indicator (111) (FIG. 6D) can comprise a wheel(64). When the second component is flowing through, the wheel can rotateas indicated by the directional arrow (65). A visual marker (66) can beused in combination of the flap or the wheel. In one example, a highcontrast visual marker, such as black-and-white marker, can be affixedto the wheel for easy monitoring of the wheel rotation. The wheel itselfcan also be made with patterns so a stationary wheel and a rotatingwheel can be easily distinguished. Commercial flow indicators can besuitable.

The electronic flow indicator can comprise one or more flow sensors(67). In one example, the electronic flow indicator (112) (FIG. 6E) cancomprise the one or more flow sensors, one or more signal output devices(68), such as a visual or audio signal device; and at least one powersource (69). The electronic flow indicator can be configured to producesignal, such as visual or audio signals, when the second component isflowing through.

The electronic flow indicator can also be configured to produce signal,such as visual or audio signals, when the second component is notflowing through.

This invention is further directed to a kit for converting a spray gunto spray a coating composition having a first component and a secondcomponent. The kit can comprise:

(a) a hollow spray needle (9) having a longitudinal channel (9 a)therein, a channel opening (13 a) at one end of said hollow sprayneedle, and a second inlet (8) at the other end of said hollow sprayneedle distal to said channel opening (13 a);

(b) an inlet valve for controlling said second inlet (8); and

(c) a detachable coupling assembly (18), wherein:

when assembled to said spray gun, at least a portion of said hollowspray needle (9) is housed in a tubular nozzle casing (6) andfunctionally coupled to a trigger (22) of said spray gun, and saidhollow spray needle (9) is configured to slide in said tubular nozzlecasing (6) between a spray position and a closed position as controlledby said trigger (22); said second inlet (8), said inlet valve and saiddetachable coupling assembly (18) are configured so that said secondinlet is open at said spray position and is closed at said closedposition.

The inlet valve can be selected from a pin valve, a sliding valve, or acombination thereof, as described above. The pin valve can comprise aseal pin (16) that is positioned at the second inlet (8) with at least aportion of the seal pin seated within the second inlet (8) perpendicularto the hollow spray needle.

Any of the aforementioned detachable coupling assembly can be suitablefor the kit. The detachable coupling assembly, as described above, canbe assembled externally to said spray gun body.

The kit can further comprise the aforementioned flow indicator (11 b).

This invention is further directed to a two-component spray guncomprising the kit of this invention or modified by the kit of thisinvention.

One advantage of this invention is that an existing conventional spraygun typically used for spraying a single component can be easilyconverted to a two-component spray gun for spraying two components. Thehollow spray needle can replace a conventional needle of an existingconventional spray gun. The frame and the valve coupling can be easilyattached externally to the existing conventional spray gun without majorchange in the structure of the existing conventional spray gun.

This invention is further directed to a method for producing a layer ofa coating composition comprising a first component and a secondcomponent on a substrate. The method can comprise the steps of:

i) providing a spray gun comprising:

-   -   (A) a spray gun body (1) comprising a carrier inlet (12), a        first inlet (10) connected to a first connection path (10 a);    -   (B) a tubular nozzle casing (6) having a nozzle (13), said        tubular nozzle casing being housed within said spray gun body        (1);    -   (C) a hollow spray needle (9) having a longitudinal channel (9        a) therein, a channel opening (13 a) at one end of said hollow        spray needle, and a second inlet (8) at the other end of said        hollow spray needle distal to said channel opening (13 a),        wherein said hollow spray needle (9) is partially positioned and        is slidable in said tubular nozzle casing (6) between a spray        position and a closed position;    -   (D) an inlet valve for controlling said second inlet (8); and    -   (E) a detachable coupling assembly (18) affixed externally to        said spray gun body distal to said nozzle; wherein said second        inlet (8), said inlet valve and said detachable coupling        assembly are configured so that said second inlet is open at        said spray position and is closed at said closed position;    -   wherein:    -   said first component and said second component are maintained        separated in said spray gun;    -   said first inlet is configured to receive said first component        by gravity and connected to said first connection path that is        further connected to a spray passage defined by said tubular        nozzle casing and said hollow spray needle for conveying said        first component to said nozzle; and    -   said second inlet is configured to receive said second component        by gravity and connected to said longitudinal channel for        conveying said second component to said nozzle when said hollow        spray needle is at said spray position;

ii) providing the first component of said coating composition to thefirst inlet and the second component of said coating composition to saidsecond inlet;

iii) producing atomized said first component and atomized said secondcomponent to form an atomized coating mixture by supplying a pressurizedcarrier to said carrier outlet through said carrier inlet and slidingsaid hollow spray needle to said spray position; and

iv) applying said atomized coating mixture over said substrate formingsaid layer thereon.

The method can further comprise the step of curing said layer of saidcoating composition. The coating composition can be cured at ambienttemperatures, such as in a range of from 15° C. to 35° C., or atelevated temperatures, such as in a range of from 35° C. to 400° C.

The pressurized carrier can be selected from compressed air, compressedgas, compressed gas mixture, or a combination thereof. The substrate canbe a vehicle, vehicle body, or vehicle body parts.

The coating composition can be selected from a lacquer coatingcomposition, a chemical curable coating composition, a radiation curablecoating composition, or a chemical and radiation dual-cure coatingcomposition. In one example, the first component can comprise acrosslinkable and a crosslinking component and said second componentcomprises a catalyst or a latent catalyst. In another example, the firstcomponent can also comprise a radiation curable component and the secondcomponent can comprise a photo initiator. In yet another example, thefirst component can comprise a crosslinkable component, a crosslinkingcomponent and a radiation curable component, and said second componentcan comprise a catalyst, an initiator, a radiation activator, or acombination thereof. In yet another example, the first component cancomprise a crosslinkable component and said second component cancomprise a crosslinking component. In yet another example, the firstcomponent can comprise a radiation curable component and a crosslinkablecomponent, and the second component can comprise a crosslinkingcomponent. In yet another example, the first component can compriseprotected crosslinkable groups and a crosslinking component, and thesecond component can comprise water and optionally an acid. In yetanother example, the first component can comprise protectedcrosslinkable groups, and the second component comprises a crosslinkingcomponent, water, and optionally an acid. In yet another example, thesecond component can be selected from a catalyst, an initiator, anactivator, a radiation activator, a curing agent, or a combinationthereof. In yet another example, the coating mixture can have a coatingviscosity that is increasing upon time and the first component and thesecond component can be at essentially constant individual viscosityupon time.

Another advantage of this invention can include the ability forcontrolling viscosity of a coating composition. The coating mixture canhave a coating viscosity that is increasing upon time, while the firstcomponent and the second component can be at essentially constantindividual viscosity. That means that the first component and the secondcomponent can be at an individual viscosity essentially constant at thebeginning and the end of spray operation. This can be particularlyuseful for spraying coating compositions that viscosity increases veryrapidly if all components are mixed together. By utilizing thisinvention, individual components of such coating compositions can bemixed after atomization. The viscosity of individual component can beessentially constant during spray operation.

This invention can further be directed to a method for controllingviscosity of a coating composition comprising a first component and asecond component, wherein said first component reacts with said secondcomponent causing increasing viscosity of said coating composition. Themethod can comprise the steps of:

i) providing a two-component spray gun comprising:

(A) a spray gun body (1) comprising a carrier inlet (12), a first inlet(10) connected to a first connection path (10 a);

(B) a tubular nozzle casing (6) having a nozzle (13), said tubularnozzle casing being housed within said spray gun body (1);

(C) a hollow spray needle (9) having a longitudinal channel (9 a)therein, a channel opening (13 a) at one end of said hollow sprayneedle, and a second inlet (8) at the other end of said hollow sprayneedle distal to said channel opening (13 a), wherein said hollow sprayneedle (9) is partially positioned and is slidable in said tubularnozzle casing (6) between a spray position and a closed position;

(D) an inlet valve for controlling said second inlet (8); and

(E) a detachable coupling assembly (18) affixed externally to said spraygun body distal to said nozzle; wherein said second inlet (8), saidinlet valve and said detachable coupling assembly are configured so thatsaid second inlet is open at said spray position and is closed at saidclosed position;

wherein:

said first component and said second component are maintained separatedin said spray gun;

said first inlet is configured to receive said first component bygravity and connected to said first connection path that is furtherconnected to a spray passage defined by said tubular nozzle casing andsaid hollow spray needle for conveying said first component to saidnozzle; and

said second inlet is configured to receive said second component bygravity and connected to said longitudinal channel for conveying saidsecond component to said nozzle when said hollow spray needle is at saidspray position;

ii) providing the first component of said coating composition to thefirst inlet and the second component of said coating composition to saidsecond inlet;

iii) producing atomized said first component and atomized said secondcomponent to form an atomized coating mixture by supplying a pressurizedcarrier to said carrier outlet through said carrier inlet and slidingsaid hollow spray needle to said spray position; and

iv) applying said atomized coating mixture over said substrate formingsaid layer thereon;

wherein said coating mixture has a coating viscosity that is increasingupon time and said first component and said second component are atessentially constant individual viscosity upon time.

This invention is further directed to a method for converting a singlecomponent spray gun to a two-component spray gun. The method cancomprise the steps of:

1) providing a hollow spray needle (9) having a longitudinal channel (9a) therein, a channel opening (13 a) at one end of said hollow sprayneedle, and a second inlet (8) at the other end of said hollow sprayneedle distal to said channel opening (13 a);

2) providing an inlet valve for controlling said second inlet (8); and

3) providing a detachable coupling assembly (18), and

4) assembling said hollow spray needle (9), the inlet valve and saiddetachable coupling assembly (18) to said spray gun so that at least aportion of said hollow spray needle (9) is housed in a tubular nozzlecasing (6) and functionally coupled to a trigger (22) of said spray gun,and said hollow spray needle (9) is configured to slide in said tubularnozzle casing (6) between a spray position and a closed position ascontrolled by said trigger (22); said second inlet (8), said inlet valveand said detachable coupling assembly (18) are configured so that saidsecond inlet is open at said spray position and is closed at said closedposition. The detachable coupling assembly (18) can comprise theaforementioned frame, the second connection coupling, the valvecoupling, and the one or more fasteners.

The substrate can be wood, plastic, leather, paper, woven and nonwovenfabrics, metal, plaster, cementitious and asphaltic substrates, andsubstrates that have one or more existing layers of coating thereon. Thesubstrate can be vehicle body or vehicle parts thereof.

Although coating compositions with multiple coating components arespecifically described here, this invention can also be used for acomposition having multiple components that need to be mixed to form amixed composition. With this invention, a first component of thecomposition can be atomized by a spray device and a second or asubsequent component of the composition can be siphoned into theatomized first component to form the mixed composition.

What is claimed is:
 1. A spray gun for spraying a coating compositionhaving a first component and a second component, said spray guncomprising: (A) a spray gun body comprising a carrier inlet, a firstinlet connected to a first connection path; (B) a tubular nozzle casinghaving a nozzle, said tubular nozzle casing being housed within saidspray gun body; (C) a hollow spray needle having a longitudinal channeltherein, a channel opening at one end of said hollow spray needle, and asecond inlet at the other end of said hollow spray needle distal to saidchannel opening, wherein said hollow spray needle is partiallypositioned and is slidable in said tubular nozzle casing between a sprayposition and a closed position; (D) an inlet valve for controlling saidsecond inlet; and (E) a detachable coupling assembly affixed externallyto said spray gun body distal to said nozzle; wherein said second inlet,said inlet valve and said detachable coupling assembly are configured sothat said second inlet is open at said spray position and is closed atsaid closed position; wherein: said first component and said secondcomponent are maintained separated in said spray gun such that saidfirst component and said second component remain separated until sprayedout of said nozzle; said first inlet is configured to receive said firstcomponent by gravity and connected to said first connection path that isfurther connected to a spray passage defined by said tubular nozzlecasing and said hollow spray needle for conveying said first componentto said nozzle; and said second inlet is configured to receive saidsecond component by gravity and connected to said longitudinal channelfor conveying said second component to said nozzle when said hollowspray needle is at said spray position.
 2. The spray gun of claim 1,wherein said detachable coupling assembly comprises a second connectioncoupling for connecting to a second reservoir; and wherein saidlongitudinal channel is configured to disconnect from said secondconnection coupling when said hollow spray needle is at said closedposition.
 3. The spray gun of claim 1, wherein said spray passage isconfigured to disconnect from said first connection path when saidhollow spray needle is at said closed position.
 4. The spray gun ofclaim 2, wherein said longitudinal channel is configured to disconnectfrom said second connection coupling and said spray passage isconfigured to disconnect from said first connection path when saidhollow spray needle is at said closed position.
 5. The spray gun ofclaim 1 further comprising a main reservoir for conveying said firstcomponent to said first inlet by gravity.
 6. The spray gun of claim 1further comprising a second reservoir for conveying said secondcomponent to said second inlet by gravity.
 7. The spray gun of claim 1further comprising a flow control means coupled to the second inlet forregulating flow of the second component.
 8. The spray gun of claim 1,wherein said tubular nozzle casing or said hollow spray needle has atapered opening at the nozzle.
 9. The spray gun of claim 1, wherein thehollow spray needle is configured to seal the nozzle at said closedposition.
 10. The spray gun of claim 1, wherein said detachable couplingassembly comprises a frame, a second connection coupling, a valvecoupling, and one or more fasteners.
 11. The spray gun of claim 1,wherein said inlet valve is selected from a pin valve, a sliding valve,or a combination thereof.
 12. A kit for converting a spray gun to spraya coating composition having a first component and a second component,said kit comprising: (a) a hollow spray needle having a longitudinalchannel therein, a channel opening at one end of said hollow sprayneedle, and a second inlet at the other end of said hollow spray needledistal to said channel opening, wherein said hollow spray needle isconfigured to be housed in a tubular nozzle casing of said spray gun;(b) an inlet valve for controlling said second inlet, wherein saidsecond inlet is configured to receive said second component forconveying said second component within said hollow spray needle to anozzle; (c) a detachable coupling assembly; and (d) a first inletconnected to a first connection path that is further connected to aspray passage defined by said tubular nozzle casing and said hollowspray needle for conveying said first component to said nozzle, whereinsaid first inlet is configured to receive said first component, wherein:when assembled to said spray gun, at least a portion of said hollowspray needle is housed in said tubular nozzle casing and functionallycoupled to a trigger of said spray gun, and said hollow spray needle isconfigured to slide in said tubular nozzle casing between a sprayposition and a closed position as controlled by said trigger; saidsecond inlet, said inlet valve and said detachable coupling assembly areconfigured so that said second inlet is open at said spray position andis closed at said closed position, and wherein said spray gun isconfigured to separately maintain said first component and said secondcomponent and spray said first component and said second component outof said nozzle separately.
 13. The kit of claim 12, said inlet valve isselected from a pin valve, a sliding valve, or a combination thereof.14. The kit of claim 13, wherein said pin valve comprises a seal pinthat is positioned at the second inlet with at least a portion of theseal pin seated within the second inlet perpendicular to the hollowspray needle.
 15. The kit of claim 12, wherein said detachable couplingassembly is assembled externally to said spray gun body.
 16. The kit ofclaim 12, wherein said detachable coupling assembly comprises a frame, asecond connection coupling, a valve coupling, and one or more fasteners.17. The kit of claim 16, wherein said valve coupling is selected from awedge valve coupling, a sliding valve coupling, or a combinationthereof.
 18. The kit of claim 12 further comprising a flow indicator.19. The kit of claim 18, wherein said flow indicator is selected from avisual flow indicator, an electronic flow indicator, or a combinationthereof.
 20. A two-component spray gun comprising the kit of claim 12.